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| United States Patent |
5,656,405
|
|
Tsushima
|
August 12, 1997
|
Organic photoconductor for electrophotography
Abstract
An organic photoconductor for electrophotography that is light in weight,
yields excellent images and is easily disposed of, which comprises a
cylindrical conductive substrate that contains cross-linked polyphenylene
sulfide as its main component, a blocking layer that contains melamine
resin as its main component formed on the conductive substrate, a charge
generation layer formed on the blocking layer, and a charge transport
layer formed on the charge generation layer.
| Inventors:
|
Tsushima; Akane (Tokyo, JP)
|
| Assignee:
|
Fuji Electric Co., Ltd. (Kawasaki, JP)
|
| Appl. No.:
|
583495 |
| Filed:
|
January 5, 1996 |
Foreign Application Priority Data
| Current U.S. Class: |
430/58.75; 430/58.4; 430/59.2; 430/59.4; 430/64; 430/65; 430/69 |
| Intern'l Class: |
G03G 005/14 |
| Field of Search: |
430/64,65,69,59,58
|
References Cited
U.S. Patent Documents
| 5229239 | Jul., 1993 | Yu.
| |
| 5512399 | Apr., 1996 | Kawata et al. | 430/69.
|
| 5556728 | Sep., 1996 | Nogami et al. | 430/64.
|
| Foreign Patent Documents |
| 58-63945 | Apr., 1983 | JP.
| |
| 59-154460 | Sep., 1984 | JP.
| |
Other References
Borsenberger, Paul M. and David Weiss. Organic Photoreceptors for Imaging
Systems. New York: Marcel-Dekker, Inc. pp. 289-292. 1993.
|
Primary Examiner: Rodee; Christopher D.
Attorney, Agent or Firm: Morrison Law Firm
Claims
What is claimed is:
1. An organic photoconductor for electrophotography comprising:
a cylindrical conductive substrate made of a plastic material;
said cylindrical conductive substrate containing at least 50% by weight of
a cross-linked polyphenylene sulfide;
a blocking layer formed on said conductive substrate, said blocking layer
containing at least 50% by weight melamine resin;
a charge generation layer formed on said blocking layer; and
a charge transport layer formed on said charge generation layer.
2. An organic photoconductor for electrophotography according to claim 1
wherein said blocking layer containing about 87.7% by weight melamine
resin, about 10.5% by weight iodine, and about 1.7% by weight silicon
oxide.
3. An organic photoconductor for electrophotography according to claim 2
wherein said blocking layer is about 10 .mu.m thick.
4. An organic photoconductor for electrophotography according to claim 1
wherein said blocking layer containing about 89.3% by weight melamine
resin, and about 10.7% by weight iodine.
5. An organic photoconductor for electrophotography according to claim 4
wherein said blocking layer is about 10 .mu.m thick.
6. An organic photoconductor for electrophotography according to claim 1
wherein said charge generation layer containing at least 50% by weight
organic material.
7. An organic photoconductor for electrophotography according to claim 1
wherein said charge generation layer containing about 50% by weight metal
free phthalocyanine and about 50% by weight poly(vinyl butyral).
8. An organic photoconductor for electrophotography according to claim 7
wherein said charge generation layer is about 0.3 .mu.m thick.
9. An organic photoconductor for electrophotography according to claim 1
wherein said charge generation layer containing about 50% by weight azo
pigment having the formula:
##STR2##
and about 50% by weight poly(vinyl butyral).
10. An organic photoconductor for electrophotography according to claim 1
wherein said charge transport layer containing at least 50% by weight
organic material.
11. An organic photoconductor for electrophotography according to claim 1
wherein said charge transport layer is a compound having a structure shown
in the formula:
##STR3##
12. An organic photoconductor for electrophotography according to claim 1
wherein said charge transport layer containing about 50% by weight
hydrazone and about 50% by weight polycarbonate.
13. An organic photoconductor for electrophotography according to claim 12
wherein said charge transport layer is formed to a thickness up to about
20 .mu.m.
14. An organic photoconductor for electrophotography comprising:
a cylindrical conductive substrate made of a plastic material;
said cylindrical conductive substrate containing a cross-linked
polyphenylene sulfide as a main component;
a blocking layer formed on said conductive substrate;
said blocking layer containing melamine resin as a main component;
a charge generation layer formed on said blocking layer;
said charge generation layer containing organic material as a main
component; and
a charge transport layer formed on said charge generation layer, wherein
said charge transport layer containing organic material as a main
component.
Description
BACKGROUND OF THE INVENTION
The present invention relates to organic photoconductors for
electrophotography. More specifically, the present invention relates to
organic photoconductors which use a cylindrical conductive substrate made
of plastic material.
Recently, the so-called function-separation type organic photoconductors
have been developed for electrophotography and put into market. As
disclosed in the Japanese Examined Patent Publications No. S55-42380 and
No. S60 34099, the function-separate type organic photoconductors have a
charge generation layer on a conductive substrate, and a charge transport
layer on the charge generation layer.
The charge generation layer and the charge transport layer contain organic
materials as their main component. Usually, an aluminum alloy cylinder is
used for the conductive substrate.
The charge generation layer is formed on the conductive substrate by
coating and drying a coating liquid. The coating liquid consists of an
organic solvent in which an organic charge generation agent together with
a resin binder are dispersed and dissolved.
The charge transport layer is formed on the charge generation layer by
coating and drying a coating liquid which consists of an organic solvent
in which an organic charge transport agent together with a resin binder
are dispersed and dissolved. If necessary, an antioxidant may be added to
the charge transport layer.
However, image defects often occur in the above described conventional
photoconductors. In more detail, image defects such as voids and grease
streaks (greasing) are often caused in the normal development type
electrophotographic apparatuses. Development type electrophotographic
apparatuses are exemplified by plain paper copiers. Further, printing
detects such as black spot and lowered contrast that frequently occur
after repeated printing are often caused in the reversal development type
electrophotographic apparatus. Reversal development type
electrophotographic apparatus are exemplified by laser printers.
In addition, aluminum alloys used for photoconductor substrates can cause
other problems. Recently, the detergent for cleaning the substrate has
been switched from conventional freon detergents to aqueous detergents due
to the environmental considerations such as causing the diminution of
ozone in the atmosphere. However, image defects are caused by deposit
residues remaining on aluminum alloys cleaned with aqueous detergents.
When the aluminum alloy substrate is coated with the charge generation
layer and the charge transport layer, uneven coating is often caused by
the high thermal conductivity of the aluminum alloy.
It is often necessary to roughen the substrate surface, form a light
absorption layer, or form an irregular-reflection layer on the substrate
to prevent interference fringes from forming on the images obtained in the
electrophotographic apparatuses such as laser printers that use a white
exposure light.
Although it has been a necessary objective to reduce the weight of the
electrophotographic apparatuses, it is nevertheless difficult to reduce
the weight of the photoconductors, since the specific gravity of the
aluminum alloy is large.
Further, since the used photoconductors must be collected by specialized
dealers, users cannot dispose of the used photoconductors easily.
OBJECTS AND SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to
provide an organic photoconductor for electrophotography that is light in
weight, facilitates obtaining excellent images, and is easily disposed of.
According to the present invention, there is provided an organic
photoconductor for electrophotography that comprises a cylindrical
conductive substrate made of plastic material containing cross-linked
polyphenylene sulfide as its main component, a blocking layer on the
conductive substrate, wherein the blocking layer contains melamine resin
as its main component, a charge generation layer formed on the blocking
layer, in which the charge generation layer contains organic material as
its main component, and a charge transport layer formed on the charge
generation layer, in which the charge transport layer contains organic
material as its main component.
Briefly stated, an organic photoconductor for electrophotography that is
light in weight, yields excellent images and is easily disposed of,
comprises a cylindrical conductive substrate that contains cross-linked
polyphenylene sulfide as its main component, a blocking layer that
contains melamine resin as its main component formed on the conductive
substrate, a charge generation layer formed on the blocking layer, and a
charge transport layer formed on the charge generation layer.
According to an embodiment of the present invention, an organic
photoconductor for electrophotography comprises a cylindrical conductive
substrate made of a plastic material, the plastic material containing at
least 50% by weight cross-linked polyphenylene sulfide, a blocking layer
on the conductive substrate, a charge generation layer on the blocking
layer, and a charge transport layer on the charge generation layer.
According to another embodiment of the present invention, an organic
photoconductor for electrophotography comprises a cylindrical conductive
substrate made of a plastic material, the plastic material containing at
least 50% by weight cross-linked polyphenylene sulfide, a blocking layer
on the conductive substrate, the blocking layer containing at least 50% by
weight melamine resin, a charge generation layer on the blocking layer,
the charge generation layer containing at least 50% by weight organic
material, and a charge transport layer on the charge generation layer,
wherein the charge transport layer containing at least 50% by weight
organic material.
According to another embodiment of the present invention, an organic
photoconductor for electrophotography comprises a cylindrical conductive
substrate made of a plastic material, the plastic material containing a
cross-linked polyphenylene sulfide as a main component, a blocking layer
formed on the conductive substrate, the blocking layer containing melamine
resin as a main component, a charge generation layer formed on the
blocking layer, the charge generation layer containing organic material as
a main component, and a charge transport layer formed on the charge
generation layer, wherein the charge transport layer containing organic
material as a main component.
The above, and other objects, features and advantages of the present
invention will become apparent from the following description read in
conjunction with the accompanying drawings, in which like reference
numerals designate the same elements.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional view of a schematic structure of the organic
photoconductor for electrophotography according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In an embodiment of the present invention, it is advantageous to adopt a
melamine resin, that is a thermosetting resin, for the material of the
blocking layer. It is preferable to set the blocking layer as a film of
melamine resin containing aromatic carboxylic acid and iodine added
thereto, and/or aromatic carboxylic anhydride and iodine added thereto.
Filler may be added to the blocking layer to prevent the formation of
interference fringes. In addition, it is preferable that the blocking
layer be about three times as thick as the surface roughness R.sub.MAX of
the substrate.
The charge generation layer is formed as a coating film of an organic
charge generation agent and a resin binder. An appropriate agent is
selected that matches the wavelength of the exposure light used in the
image formation process.
The charge transport layer is formed as a coating film that comprises at
least one organic charge transport agent such as poly(vinylcarbazole),
oxadiazole, imidazole, pyrazoline, hydrazone, stilbene, etc., and resin
binder. If necessary, an antioxidant, such as an ultraviolet ray absorbing
agent, may be added.
The substrate is a cross-linked polyphenylene sulfide. The specific gravity
of the resulting substrate is reduced compared to aluminum. Consequently,
because the cross-linked polyphenylene sulfide is the main component of
the substrate, the weight of the substrate is reduced. This substrate,
easily formed by injection molding, results with excellent dimensional
precision against deformation from chemical and thermal activity.
The substrate maintains its surface profile stably without deterioration,
even when the substrate is cleaned with an aqueous detergent. Thus, image
defects such as black spots, voids, etc. are greatly reduced. Further, the
thermal conductivity of the substrate is low. Thus, organic films may be
formed uniformly on the substrate by coating.
A further provision of the blocking layer that contains melamine resin as
its main component requires that the surface of the substrate be smooth.
Thus, the formation of organic coating films uniformly is facilitated by
the smooth surface of the substrate. Furthermore, since the charge
injection from the substrate to the charge generation layer is thus
optimized. Therefore, image defects such as voids, greasing, black spots,
and lowered image contrast from repeated use are substantially prevented
from occurring.
Referring to FIG. 1, an organic photoconductor, generally shown as 101,
includes a blocking layer 2 formed on a cylindrical conductive substrate
1. Substrate 1 contains cross-linked polyphenylene sulfide as its main
component. The blocking layer 2 contains melamine resin as its main
component. A charge generation layer 3 is formed on the blocking layer 2.
A charge transport layer 4 is formed on the charge generation layer 3.
First Embodiment
A cylindrical conductive substrate 1 (the surface roughness R.sub.MAX
thereof is about 3 .mu.m), that contains cross-linked polyphenylene
sulfide as its main component, was used in the photoconductor of the first
embodiment. A blocking layer 2 was formed on cylindrical conductive
substrate 1 by immersion coating of a coating liquid consisting of 20
weight parts of ethanol in which 50 weight parts of a melamine resin (Uban
2020 supplied from Mitsui Toatsu Chemicals Inc.) was dissolved, and to
which 6 wt. % of iodine was added. Blocking layer 2 was formed to a
thickness of 10 .mu.m by drying the coating liquid at 130.degree. C. for
20 min. Charge generation layer 3 was formed on blocking layer 2 to a
thickness of about 0.3 .mu.m by immersion coating of a coating liquid
consisting of 100 weight parts of tetrahydrofuran in which 1 weight part
of X-type metal-free phthalocyanine (FASTGEN BLUE 8120 supplied from
DAINIPPON INK & CHEMICALS INC.) and 1 weight part of poly(vinyl butyral)
were dispersed and dissolved. This layer was dried.
Charge transport layer 4 was formed on charge generation layer 3 to a
thickness of about 20 .mu.m by immersion coating of a coating liquid
consisting of 80 weight parts of tetrahydrofuran in which 10 weight parts
of a hydrazone compound (CTC 191 supplied from Anan Corporation), and 10
weight parts of polycarbonate resin (L-1225 supplied from TEIJIN LTD.)
were dissolved. This layer was dried.
The photoconductor of the first embodiment exhibits excellent sensitivity
(half decay exposure light intensity) of 0.4 J/cm.sup.2 for a beam
(wavelength 780 nm) from a semiconductor laser diode. A printing test was
conducted on the photoconductor in a commercially supplied laser beam
printer. The results of the test showed that no image defects such as
black spots were observed. Images with high printing contrast and high
resolution were obtained. Finally, no change of the printing contrast were
caused by continuous printing.
Second Embodiment
A cylindrical conductive substrate that contains cross-linked polyphenylene
sulfide as its main component was used in the photoconductor of the second
embodiment. Blocking layer 2 was formed on cylindrical conductive
substrate 1 by immersion coating of a coating liquid consisting of 20
weight parts of ethanol in which 50 weight parts of a melamine resin (Uban
20RI supplied from Mitsui Toatsu Chemicals Inc.) was dissolved, and 6 wt.
% of iodine and 1 weight part of silicon oxide (Hydrophobic Silica Gel
R-212 supplied from Nippon Aerozil Co., Ltd.) were added. This layer was
dried.
Blocking layer 2 was formed to a thickness of 10 .mu.m by drying the
coating liquid at 130.degree. C. for 20 min. Charge generation layer 3 and
charge transport layer 4 were formed successively on blocking layer 2 in
the same way as in the first embodiment.
The photoconductor of the second embodiment exhibits excellent sensitivity
(half decay exposure light intensity) of 0.4 J/cm.sup.2 for a beam
(wavelength 780 nm) from a semiconductor laser diode. A printing test was
conducted on the photoconductor in a commercially supplied laser beam
printer. The results of the test showed no image defects such as black
spots observed. High printing contrast and images of high resolution were
obtained. Further, no change of the printing contrast was caused by
continuous printing.
Third Embodiment
Cylindrical conductive substrate 1 that contains cross-linked polyphenylene
sulfide as its main component was used in the photoconductor of the third
embodiment. Blocking layer 2 was formed on cylindrical conductive
substrate 1 by immersion coating of a coating liquid consisting of 20
weight parts of ethanol in which 50 weight parts of a melamine resin (Uban
20RI supplied from Mitsui Toatsu Chemicals Inc.) was dissolved, and 6 wt.
% of iodine was added. Blocking layer 2 was formed to a thickness of 10
.mu.m by drying the coating liquid at 130.degree. C. for 20 min.
Charge generation layer 3 was formed on blocking layer 2 to a thickness of
about 0.3 .mu.m by immersion coating of a coating liquid consisting of 100
weight parts of tetrahydrofuran in which 1 weight part of an azo pigment
having a structure shown in the following formula (1) and 1 weight part of
a poly(vinyl butyral) resin (BH-S supplied from Sekisui Chemical Co.,
Ltd.) were dispersed and dissolved. Charge transport layer 4 was formed on
charge generation layer 3 to a thickness of about 20 .mu.m by immersion
coating of a coating liquid consisting of 80 weight parts of
tetrahydrofuran in which 10 weight parts of a compound having a structure
shown in the following formula (2) was dissolved.
##STR1##
The photoconductor of the third embodiment exhibits excellent sensitivity
(half decay exposure light intensity) of 0.81 lux-sec for a beam from a
halogen lamp. A printing test was conducted on the photoconductor in a
commercially supplied copying machine. As the test determined, no image
defects such as voids, etc. were observed. High printing contrast and
excellent graduation sequence were obtained.
Fourth Embodiment
Cylindrical conductive substrate 1 that contains cross-linked polyphenylene
sulfide as its main component was used in the photoconductor of the fourth
embodiment. Blocking layer 2 was formed on cylindrical conductive
substrate 1 by immersion coating of a coating liquid consisting of 20
weight parts of ethanol in which 50 weight parts of a melamine resin (Uban
2020 supplied from Mitsui Toatsu Chemicals Inc.) was dissolved, and 6 wt.
% of iodine and 1 weight part of silicon oxide (Hydrophobic Silica Gel
R-212 supplied from Nippon Aerozil Co., Ltd.) were added. Charge
generation layer 3 and charge transport layer 4 were formed successively
on the blocking layer in the same way as in the third embodiment. This
layer was dried.
The photoconductor of the fourth embodiment exhibits excellent sensitivity
(half decay exposure light intensity) of 0.81 lux-sec for a beam from a
halogen lamp. A printing test was conducted on the photoconductor in a
commercially supplied copying machine. The test showed that no image
defects such as voids, etc., were observed. High printing contrast and
excellent graduation sequence were obtained.
The organic photoconductor for electrophotography of the present invention
exhibits the following effects. By using cross-linked polyphenylene
sulfide, the specific gravity thereof is small. Consequently, because the
polyphenylene sulfide is the main component of the substrate, the weight
of the substrate is reduced.
The substrate of the invention is easily formed by injection molding with
excellent dimensional precision but with minimal chemical and thermal
deformation. Since the substrate maintains its surface profile stably
without deterioration even when the substrate is cleaned with an aqueous
detergent, the image defects such as black spots, voids, etc. are greatly
diminished. Furthermore, since the thermal conductivity of the substrate
is advantageously low, the blocking layer, the charge generation layer,
and the charge transport layer can be formed uniformly by coating on the
substrate.
By the further restriction provision of the blocking layer that requires a
melamine resin as its main component, image defects such as void,
greasing, black spots, and image contrast lowering by repeated use are
prevented from occurring.
Thus, the present invention facilitates providing organic photoconductors
for electrophotography which are light in weight and facilitate obtaining
excellent images stably.
Having described preferred embodiments of the invention with reference to
the accompanying drawings, it is to be understood that the invention is
not limited to those precise embodiments, and that various changes and
modifications may be effected therein by one skilled in the art without
departing from the scope or spirit of the invention as defined in the
appended claims.
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